If you live abroad and have your own business, you may need to file special forms with your tax return. If you own more than 10% of a foreign corporation, you may be required to file Form 5471 or pay penalties of $10,000 US for each failure to file the form. This forms reports on the ownership, income and expenses of the foreign corporation.
If you operate through a foreign partnership, you may be required to file Form 8865 which reports on the ownership, income and expenses of that partnership. Again failure to file this form can result in a $10,000 per year penalty.
If you have a foreign bank account, stock market account, or other financial accounts that any tiem during the year had more than $10,000US in it or a group of such accounts, you must file Form TDF 90.22-1 which is not filed with your tax return, but is due 6/30 of each year. It reports information on the account and its ownership.